An unnamed narrator arrives at the House of Usher, a very creepy mansion owned by his boyhood friend Roderick Usher. Roderick has been sick lately, afflicted by a disease of the mind, and wrote to his friend, our narrator, asking for help. The narrator spends some time admiring the awesomely spooky Usher edifice. While doing so, he explains that Roderick and his sister are the last of the Usher bloodline, and that the family is famous for its dedication to the arts (music, painting, literature, etc.). Eventually, the narrator heads inside to see his friend.
Roderick indeed appears to be a sick man. He suffers from an "acuteness of the senses," or hyper-sensitivity to light, sound, taste, and tactile sensations; he feels that he will die of the fear he feels. He attributes part of his illness to the fact that his sister, Madeline, suffers from catalepsy (a sickness involving seizures) and will soon die, and part of it to the belief that his creepy house is sentient (able to perceive things) and has a great power over him. He hasn’t left the mansion in years. The narrator tries to help him get his mind off all this death and gloom by poring over the literature, music, and art that Roderick so loves. It doesn’t seem to help.
As Roderick predicted, Madeline soon dies. At least we think so. All we know is that Roderick tells the narrator she’s dead, and that she appears to be dead when he looks at her. Of course, because of her catalepsy, she might just look like she’s dead, post-seizure. Keep that in mind. At Roderick’s request, the narrator helps him to entomb her body in one of the vaults underneath the mansion. While they do so, the narrator discovers that the two of them were twins and that they shared some sort of supernatural, probably extrasensory, bond.
About a week later, on a dark and stormy night, the narrator and Usher find themselves unable to sleep. They decide to pass away the scary night by reading a book. As the narrator reads the text aloud, all the sounds from the fictional story can be heard resounding from below the mansion. It doesn’t take long for Usher to freak out; he jumps up and declares that they buried Madeline alive and that now she is coming back. Sure enough, the doors blow open and there stands a trembling, bloody Madeline. She throws herself at Usher, who falls to the floor and, after "violent" agony, dies along with his sister. The narrator flees; outside he watches the House of Usher crack in two and sink into the dark, dank pool that lies before it.